The subject invention concerns the Field of Eye Diagram Rendering in general, and specifically concerns the optimized rendering of eye diagrams synchronized to a recovered clock and based on a single shot acquisition of a digital storage oscilloscope.
The rendering of Eye Diagrams on signals acquired by a Digital Storage Oscilloscope (DSO) is well known in the art. U.S. Pat. No. 5,343,405 (Kucera), issued 30 Aug. 1994 and assigned to the same assignee as the subject invention, is an early patent describing such a system.
Unfortunately, current methods used in modern DSOs for rendering eye diagrams exhibit significant deficiencies. For example, they do not support suitably high data rates relative to scope bandwidth and maximum sampling rate (currently OC-48 data rates at 2.4-2.5 Gb/s for 4 GHz bandwidth 20G samples/s oscilloscopes). In real time oscilloscopes, they are subject to instrument trigger jitter.
When used in sampling oscilloscopes these methods require periodic signals and stable clock or clock recovery. What is needed is a method of rendering of eye diagrams in a digital storage oscilloscope that overcomes the above-noted deficiencies.
In a first embodiment of the invention, a first method, suitable for use in a digital storage oscilloscope for rendering an eye diagram synchronized to a recovered clock and based on a single shot acquisition, acquires a waveform and measures the timing of its edges. It then estimates the symbol rate of the waveform and derives clock signals in accordance with the edge timing and the estimated symbol rate. The waveform data is then sliced into frames with respect to the derived clock signals, and the frames are partially overlapped and aligned to form an eye diagram.
In a second embodiment of the invention, a second method, suitable for use in a digital storage oscilloscope for rendering an eye diagram synchronized to a recovered clock and based on a single shot acquisition, acquires a waveform and measures the timing of its edges. It then estimates the symbol rate of the waveform and derives clock signals in accordance with the edge timing and the estimated symbol rate. The waveform data is then sliced into frames with respect to the derived clock signals, and the frames aligned, without being overlapped, to form an eye diagram.